ABSTRACT
Chapter 4 describes findings from the rapidly growing body of research on genetic and biological factors in depression. Accurately interpreting such research is challenging due to complexity, interactions among different processes at different levels from cells to brain structures, with often-unwarranted causal interpretations of phenomena that are likely to be correlates and consequences of depression or markers rather than causes. Nevertheless, the explosion of depression research on genetics and neuroscience provides important potential clues about mechanisms by which stress triggers depression and neural and genetic factors that promote vulnerability for depression. Genetic studies indicate moderate heritability, likely due to many genes that have small effects, and greatly influenced by environmental factors. The emphasis on stress as a trigger of depression has encouraged extensive study of neuroendocrine functioning, especially abnormal patterns in the hypothalamic pituitary adrenal (HPA) axis and the stress hormone, cortisol. Neural structures and circuits that control perceptions and interpretations of the self and the environment, and emotional reactivity and regulation are particularly relevant. Research on the hormonally-relevant phases of women’s reproductive life is discussed in relation to women’s higher rates of depression. In all aspects of the biology of depression, environmental and developmental factors play critical roles.
